Unanswered Questions

Entanglement, Teleportation, and Quantum Computing

What is quantum teleportation and how does it use entanglement?

First, what it is not. It is not “Beam me up, Scotty” where a person disappears at one place and appears at another. It involves only information transfer by either photons or atoms.

Teleportation involves an atom whose state is to be communicated from a sender, Alice, to a receiver, Bob. It also involves a source of two entangled photons.

Alice first sets or measures the state of the atom. This is the information she will send to Bob. At the same time she measures the polarization of one of the two photons. This polarization information is the encryption key that will allow Bob to decode the information. Because the two photons are entangled the polarization of the transmitted photon is fixed. Bob now has the key that allows him to decode the information Alice sent. In practice, of course, the encryption key isn’t the polarization of a single photon, but many.

The longest distance information has been teleported is 16 kilometers through the air in Beijing.